Field
Plasma-based atomic layer etching of materials may be of benefit to various semiconductor manufacturing and related technologies. For example, plasma-based atomic layer etching of materials may be beneficial for removing angstrom thick layers from a surface in advanced semiconductor manufacturing and related technologies that increasingly demand atomistic surface engineering.
Description of the Related Art
While atomic layer deposition has been tremendously successful, the development of a corresponding atomic layer etching (ALE) method has lagged. In atomic layer deposition, control of deposited film thickness near one atomic monolayer may be based on careful choice of chemical precursors which, once adsorbed at one monolayer on the substrate, passivate the surface and prevent multi-layer adsorption.
A subsequent reaction step transforms the precursor into the desired material. Experimental and computational efforts aimed at realizing a corresponding ALE approach using cyclic surface passivation followed by removal of weakly bound chemical reaction products resulting from interaction of the passivation layer with the surface have been started in the past. These efforts have shown that a key obstacle toward realizing ALE is achieving self-limited etching, in particular for situations when ion bombardment to remove the reacted material and precise control of surface coverage by the chemical precursor is required.
Self-limited etching can require both negligible spontaneous chemical etching by the precursor used to passivate the surface, and insignificant physical sputtering of the unmodified material after etch product removal. Minimizing physical sputtering has been difficult to realize consistently, and additional factors, such as, for example, photon-induced etching for plasma environments, have also been invoked in an attempt to explain persistent etching for certain conditions.